Explain some string functions of PHP

In the programming world, a string is considered a data type, which in general is a sequence of multiple characters that can contain whitespaces, numbers, characters, and special symbols. For example, "Hello World!", "ID-34#90" etc. PHP also allows single quotes(' ') for defining a string. Every programming language provides some in-built functions for the manipulation of strings. Some of the basic string functions provided by PHP are as follows:

strlen() Function

It returns the length of the string i.e. the count of all the characters in the string including whitespace characters.

Syntax

strlen(string or variable name);

Example: This example illustrates the basic implementation of the strlen() Function in PHP.

<?php 

$str = "Hello World!";

// Prints 12 as output
echo strlen($str);

// Prints 13 in a new line
echo "<br>" . strlen("GeeksForGeeks"); 

?>

Output:

12
13

strrev() Function

 It returns the reversed string of the given string.

Syntax

strrev(string or variable name);

Example: This example illustrates the basic implementation of the strrev() Function in PHP.

<?php

$str = "Hello World!";
echo strrev($str);

?>

!dlroW olleH

trim(), ltrim(), rtrim(), and chop() Functions

It removes white spaces or other characters from the string. They have two parameters: one string and another charList, which is a list of characters that need to be omitted.

• trim(): Removes characters or whitespaces from both sides.
• rtrim() & chop():  Removes characters or whitespaces from the right side.
• ltrim(): Removes characters or whitespaces from the left side.

Note: The browser output of the code given in the examples below may vary from the HTML output for these functions.

Syntax

rtrim(string, charList)
ltrim(string, charList)
trim(string, charList)
chop(string, charList)

Parameter Values

• $string: This mandatory parameter specifies the string to be checked.
• $charlist: This optional parameter specifies which characters are to be removed from the string. In case, this parameter is not provided, the following characters are removed :
  • “\0” – NULL
  • “\t” – tab
  • “\n” – new line
  • “\x0B” – vertical tab
  • “\r” – carriage return
  • ” “ – ordinary white space

Note: The parameter charList is available only in PHP version 4.1 or higher.

Example: This example illustrates the basic implementation of the trim(), ltrim(), rtrim(), and chop() Functions in PHP.

<?php

$str = "\nThis is an example for string functions.\n";

// Prints original string
echo $str;

// Removes whitespaces from right end
echo chop($str) . "<br>";

// Removes whitespaces from both ends
echo trim($str) . "<br>";

// Removes whitespaces from right end
echo rtrim($str) . "<br>";

// Removes whitespaces from left end
echo ltrim($str);

?>

This is an example for string functions.

This is an example for string functions.<br>This is an example for string functions.<br>
This is an example for string functions.<br>This is an example for string functions.

strtoupper() and strtolower() Function

It returns the string after changing the cases of its letters.

• strtoupper(): It returns the string after converting all the letters to uppercase.
• strtolower(): It returns the string after converting all the letters to lowercase.

Syntax

strtoupper(string)
strtolower(string)

Example: This example illustrates the basic implementation of the strtoupper() and strtolower() Function in PHP.

<?php

$str = "GeeksForGeeks";
echo strtoupper($str)."<br>";
echo strtolower($str);

?>

Output:

GEEKSFORGEEKS
geeksforgeeks

str_split() Function

It returns an array containing parts of the string.

Syntax

str_split(string, length);

Parameters

• string: It specifies the string to be checked, it can also be a variable name of type string.
• length: It specifies the length of each part of the string to be stored in the string, by default, it is 1. If the length is larger than the size of the string, then the complete string is returned.

Example: This example illustrates the basic implementation of the str_split() Function in PHP.

<?php

$str = "GeeksForGeeks";
print_r(str_split($str));
echo "<br>";
print_r(str_split($str, 3));

?>

Output:

Array ( 
    [0] => G 
    [1] => e 
    [2] => e 
    [3] => k 
    [4] => s 
    [5] => F 
    [6] => o 
    [7] => r 
    [8] => G 
    [9] => e 
    [10] => e 
    [11] => k 
    [12] => s 
)
Array ( 
    [0] => Gee 
    [1] => ksF 
    [2] => orG 
    [3] => eek 
    [4] => s 
) 

str_word_count() Function

It is used to return information about words used in a string like the total number of words in the string, positions of the words in the string, etc. 

Syntax

str_word_count ( $string , $returnVal, $chars );

Parameters

• $string: This parameter specifies the string whose words the user intends to count. This is not an optional parameter.
• $returnVal:The return value of str_word_count() function is specified by the $returnVal parameter. It is an optional parameter and its default value is 0. The parameter can take the below values as required:
  • 0: It returns the number of words in the string $string.
  • 1: It returns an array containing all of the words that are found in the string.
  • 2: It returns an associative array with key-value pairs, where the key defines the position of the word in the string and the value is the word itself.
• $chars: This is an optional parameter that specifies a list of additional characters which shall be considered as a ‘word’.

Example: This example illustrate the basic implementation of the str_word_count() Function in PHP.

<?php
$mystring = "Geeks for Geeks is fun";
print_r(str_word_count($mystring));
?>

Output:

5

strpos() Function

This function helps us to find the position of the first occurrence of a string in another string.

Syntax

strpos(original_str, search_str, start_pos);

Parameters

Out of the three parameters specified in the syntax, two are mandatory and one is optional. The three parameters are described below:

• original_str: This is a mandatory parameter that refers to the original string in which we need to search for the occurrence of the required string.
• search_str: This is a mandatory parameter that refers to the string that we need to search.
• start_pos: This is an optional parameter that refers to the position of the string from where the search must begin.

Example: This example illustrate the basic implementation of the strpos() Function in PHP.

<?php
  
// PHP code to search for a specific string's position
// first occurrence using strpos() case-sensitive function
function Search($search, $string)
{
    $position = strpos($string, $search, 5);
    if (is_numeric($position))
    {
        return "Found at position: " . $position;
    }
    else
    {
        return "Not Found";
    }
}

// Driver Code
$string = "Welcome to GeeksforGeeks";
$search = "Geeks";
echo Search($search, $string);
?>

Output:

Found at position: 11

str_replace() Function

It is used to replace all the occurrences of the search string or array of search strings by replacement string or array of replacement strings in the given string or array respectively. 

Syntax

str_replace ( $searchVal, $replaceVal, $subjectVal, $count );

Parameters

This function accepts 4 parameters out of which 3 are mandatory and 1 is optional. All of these parameters are described below:

• $searchVal: This parameter can be of both string and array types. This parameter specifies the string to be searched and replaced.
• $replaceVal: This parameter can be of both string and array types. This parameter specifies the string with which we want to replace the $searchVal string.
• $subjectVal: This parameter can be of both string and array types. This parameter specifies the string or array of strings that we want to search for $searchVal and replace with $replaceVal.
• $count: This parameter is optional and if passed, its value will be set to the total number of replacement operations performed on the string $subjectVal.

Example: This example illustrate the basic implementation of the str_replace() Function in PHP.

<?php
  
// Input string
$subjectVal = 
      "Computer Science in GeeksforGeeks is fun";

// Using str_replace() function
$resStr = 
      str_replace('Science', 'algorithms', $subjectVal);
print_r($resStr);
?>

Output:

Computer algorithms in GeeksforGeeks is fun

ucwords() Function

It is used to convert the first character of every word in a string to upper-case.

Syntax

string ucwords ( $string, $separator )

Parameters

This function accepts two parameters out of which the first is compulsory and the second is optional. Both of the parameters are explained below:

• $string: This is the input string of which you want to convert the first character of every word to uppercase.
• $separator: This is an optional parameter. This parameter specifies a character that will be used as a separator for the words in the input string. For example, if the separator character is ‘|’ and the input string is “Hello|world” then it means that the string contains two words “Hello” and “world”.

Example: This example illustrate the basic implementation of the ucwords() Function in PHP.

<?php
  
// Original string
$str = "Geeks for geeks is fun";

// String after converting first character
// of every word to uppercase
$resStr = ucwords($str);
print_r($resStr);

?>

Output:

Geeks For Geeks Is Fun